Key controlled and power operated machine



s'. A. SWANSON 1,842,883

KEY CONTROLLED AND POWER OPERATED MACHINE 5 Sheets-Sheet 1 Jan. 26, 1932.

Filed July 10. 1929 2722:7220? or Q. Swanson SaZZ/Q 7 Jan. 26, 1932. s. A. SWANSON 1,842,883

KEY CONTROLLED AND POWER OPERATED MACHINE Filed July 10, 1929 5 Sheets-Sheet 2 n n nll n n nlln T 'ZZI 17 .f I 'I IL IN T wile-16 5';

Jan. 26, 1-932. 5. A. SWANSON 1,842,883

KEY CONTROLLED AND POWER OPERATED MACHINE Filed July 10) 1929 5 Sheets-Sheet 3 0 7 a ww n 6 sl w w Km 5 06 a I\W mm W f mS 4 a 5 w 4 Q J M 23 a \9 31% wf w d v! m 0 m- 7 w o fw 5 u a i n v/ a 0 0 q M 4 m A m U 5 o o N w y" YA U o o \k Hm m T A .N H J M w J H A v Q U 0 Q l m Y k m m H a 0\@ ib 4 5 w f 4 a Q 0 6 Y J w 0 J 5/ M M U m7 6 s. A. SWANSON 1,842,883

KEY CONTROLLED AND POWER OPERATED MACHINE Filed July 10, 1929 6 Sheets-Sheet 4 Jan. 26, 1932.

By /M" 7 a@5- Jan. 26, 1932. $-.'A. SWANSON 1' 1,842,883

KEY CONTROLLED AND POWER OPERATED 5 Sheets-Sheet 5 Filed July 10, 1929 Se Zzrz' oz" we Patented Jan. 26, 1932" SELVIYOR A. SWANSON, OF CHICAGO, ILLINOIS KEY conrnotrnn Ann rowan: OPERATED MAcnmn Application fil-c d. July 10,

The invention relates to pneumatic mechanism operableto control key actuated means, and more particularly it relates to pneumatic mechanism op'erabiy to selectively drive the "iidivi'du al actuating keys of machine such a typewriter or similarly actuated mechanism.

The invention is shown comprising a pneumatic actuator for typewriting and billing machines, but is equally as well adapted for with any other key actuated machine on mechanism. V

In typewriti ng it is frequently desirable to produce a maximum number of carbon copieswith one machine and in order that all out the copies be legible, the operator must stri re the keys with greater forcethan where only one or two copies are to be. produced. Not only is this tiresomefor the operator but it. tends to unequal weight of typing, since it is dilhcult, if not impossible, to manually strike the keys with uniform force over a prolonged period, particularly when such force isabove that normally used or required.

" The necessity for heavy strokes not only causes lack of uniformity in the typing but it tends to slow up the speed of the typing because of the physical impossibility for the operator to continue such heavystrokes at a rapid for long periods oi time. I

lrn bject, generally, of the invention, is the provision of apneu-matic actuator for machines of the kind described, which enables the oeerative in charge of the machine, by the expenditure of a minim-um oi eil-ort,- to cause the actuatorto selectively drivethe individ ual keys of the machine with any desired predetermined force.

lhe invention takes the form of pneumatic power mechanism which connects a control key board, manually manipulated by theoperative, with one or more typewriting or billing machines. The keys of the control key board a e preferably duplicates of the keys of the machine key board; the key levers of the duplicate key board are" preferably constructed for manual manipulation by uniform rela' Lively light strokes. The operative, by light- 1y striking a key of the duplicate key board; causes the pneumaticmechanism to drive the 1929'. -Serial No; 377,196.

corresponding key lever of the machine, thereby driving the lever to strike with any 1g redetermined degree of force".

A particular object of the invention is the provision of a pneumatic actuator for typewriting machines, billing machines and the like, which enables the operative, by the use of a duplicate or a control keyboard to cause the pneumatic actuator to selectively drive the individual key levers of the machine with predetermined force, the duplicate key board being: manually operable by substantially u-nitorm and equal relatively light strokes.

The pneumatic actuator is so constructed that a light stroke on one" of the keys of the duplicate key board will instantaneously cause the corresponding machine key lever to strike and immediately fall away. Until the particular duplicate key lever thus struckreturns to its normal position, the striking of any of the other keys comprising the duplica'te key board will be inefiect-ive to actuate the correspondingmachine key levers. This provision eliminates the possibility of locking the type as sometimes occurs in manual operation of the machine when two keys are accidentally struck substantially simultaneously Still another particular object is the provision of mechanism of the kind described which eliminates the possibility of interlockingtwo' or more of the types forming a part of the typewriting machine.

The pneumatic mechanism is also adapted forop'erative connection with a plurality of typewriti-ng and billing machines thereby enablingan operative,,by actuatii'ig a single duplicate key board, to cause the mechanism to simultaneously and selectively actuate the key levers of each of the machines. The number of copies of the typing thatmay be produced by a single operative is thus thereby multiplied by the number of machines connected with and simultaneously operated by the pneumatic mechanism.

A still lumber object of the invention is the provision oi a pneumatic actuator of the kind described which is: cont-rolled by a single duplicatekeyboard and capable of being con uectedwith plurality of typewriting or billing machines to cause the simultaneous selective actuation of each of the machines.

The invention has among its other objects the production of a pneumatic actuator of the rind described, w iich is relatively simple in construction, convenient, durable, and satisfactory for use wherever found applicable.

Many other objects and advantages of the construction show. will be obvious to those skilled in the art from the disclosure herein given.

To this end my invention consists in the novel construction arrangement and combination of parts herein described and shown, and more particularly pointed out in the claims.

In the drawings, wherein like reference characters indicate like or corresponding parts:

Fig. 1 is a transverse elevational' and partial sectional view of one embodiment of the invention;

F 2 is a plan view of the device shown in Fig. 1;

Fig. 2) is a section along the line 3-3 of F ig. 2 drawn to a larger scale;

Fig. 4 is a view along the line 44 of Fig. 1 showing a plan of the pneumatic action comprising a portion of my invention;

Fig. 5 is an elevational and partial sectional view of the pneumatic action shown in Fig. 4;

Fig. 6 is a section along the line 6-6 of Fig. 4;

Fig. 7 1s a section along the line 7. of Fig. 5;

8 is a transverse elevational view of a mqdified form of the invention;

Fig. 9 is a plan view of still another embodiment of the invention;

Fi 10 is a transverse view of a portion of the device shown in Fig. 9; and

Figs. 11 and 12 are detail views of a device for fastening a typewriting machine to a desk or the like.

Referring now to the drawings, 10 represents a standard typewriter fixedly mounted upon a table 11 by means of a plurality of fastening blocks 117. The typewriter 10 is provided with a standard key board 12 which is operatively connected with a manual or duplicate key board 13 in a manner hereinafter more particularly described. The duplicate key board 13 is preferably mounted in front of and on the same table as the typewriter 10, although it may be conveniently mounted on any other table providing the typewriter can be seen easily by the operator of the duplicate keyboard. The key board 12 comprises a plurality of keys 14 each mounted on a key lever 15. The duplicate key board 13 comprises a plurality of keys 16 similarly mounted on key arms 17, there being a corresponding key 16 and key arm 17 for each key 14 and key lever 15. The typewriter 10 is provided with the usual spacer bar 18 and the duplicate key board 13 is similarly equipped with a corresponding bar 19. The typewriter key board 12 is also provided with a pair of shift keys 20 and the duplicate key board 13 is similarly equipped with a pair of shift keys 21. In addition to the standard key levers 15 the typewriter 10 is also provided with a tabulator punch key 24.

A bell crank lever 26 is positioned underneath the table 11 and is pivotally mounted on a member 27. The upper end of the lever 26 projects through an aperture 84 in the table and is normally in contact with the end of the tabulator punch key 24 when the key is in its extended position. The member 27, on which the lever 26 is mounted, is fastened to the table 11 by a plurality of screws 28.

A pneumatic actuator generally designated by the numeral 29, connects the standard typewriter key board 12 with the duplicate key board 13 so that actuation of any key and key arm of the duplicate key board selectively actuates the corresponding key and key lever of the typewriter key board. The pneumatic actuator 29 comprises a plurality of power pneumatics 30, each operatively connected with one of the typewriter key levers 15.

The pneumatics 30 are operatively connected with the key levers 15 by a plurality of vertically extending rods 37 each having an upper end hooked over one of the levers l5 and its lower end projecting through a bar 41. The bars 41 are each mounted on a pneumatic 30 so as to be moved with the collapsible portion of the pneumatic. A nut is threaded onto the lower end of each of the rods 37 for the purpose of normally holding the pneumatic 30 in expanded condition and to permit the effective length of the rod to be changed and thereby adjust the force with which the collapse of the pneumatic actuates the key lever to which it is attached.

The bell crank lever 26, which cooperates with the tabulator punch key 24, is connected with one of the power pncumatics 30 by a rod 38. The rod 38 has a nut 40 threaded on each of its ends for the purpose of regulating the action of the tabulator punch key. It is obvious that collapse of the pneumatic 30, with which lever 26 is connected, will force the tabulator punch key 24 inwardly and that collapse of each of the other pneumatics 30 will cause the corresponding key levers 15 to which they are attached to be actuated downwardly by a quick decisive stroke.

The power pneumatics 30 are positioned underneath the table 11 and require the provision of an aperture 39 through the table 11 to accommodate the rods 8? connecting the pneumatics with the key levers 15. The power pneumatics 30 are supported by oppositely positioned walls or frames 35 fastened by any suitable means to thejunder side of the table 11. v

The pneumatics 30: are shown. as arranged in four rows corresponding to the rows of typewriter key levers 15. All of the pneumatics 30 of any one roware for convenience connect-ed with a corresponding key lever in the same row. Each of the pneumati-cs comprising a row are operatively connected with the same pneumatic section or bank of which there are four, numbered 31, 32, 33 and 34. Each of the sections or banks 31, 32, 33, and 34 are fastened to the walls or frames 35 by a plurality of screws 36, as, best shown in Fig. 1.

A. closed chamber 42, extending substantially the full length of each of. the sections or banks 31, 32, 33 and34 is normally maintained at reduced air pressures by connection with a pump (not shown). Each of the pneumatics 30 isconnected with a chamber 42 by a passage Eachpassage 45' is controlled by a double valve 43, shown closed in Fig. 1. in which position the passage 45 connects the interior of the penumatic 30 with the atmospheric through a plurality of ports 146. A plurality of pallets 44 are positioned in each of the chambers 42. The pallets44 are each connected with one of the ducts 57 to control the opening and closing of the corresponding valve 43. In the closed position of the, valve 43, a plate 143 presses against a centrally apertured partition plate 145 and thereby closes the partition plate to the passage of air. The plate 145 is apertured to, receive the stem 147 of the valve 43. The interior of, the pneumatic 30 is connected by the passage 45 and the ports 146 with the atmosphere when the valve 43 is closed. Atmospheric pressure in the duct 57 will flatten the pallet 44 and'cause the valve 43 to open. In the open position of the valve 43, the plate 144v-closes the ports 146 and the plate 143 is unseat-ed from the apertu-red partitioned plate 145 The. interior of the pneumatic 30 is thus connected through the passage 45. with the chamber 42-. Since the chambers 42 are normally at reduced air pressure, it is obvious. that anything operating to openthe valve 43 of an individual pneumatic 30 will reduce the pressure within the pneumatic and cause its collapse. Such collapse of a pneumatic 310 will actuate the particular typewriter key lever 15 with which the pneumatic is connected by a rod 37' or 38.

1'; control action 46 forming part of the actuator 29, connects the duplicate key board 13 with the various pneumatics 30 so that actuation of a particular lrey arm 17 of the duplicate key board will cause the actuation of the corresponding key lever 15 of the typewriter 10 by reason of the resultant collapse of the pneumatic 30' with which the actuatedkey lever is, connected by a. rod, 37 For-this pur-.

pose the key armsl'Z are each mounted on the scribed above.

under side of one of a plurality of overlapping transversely extending blocks 65 and block The blocks 65 and the block 66 are rigidly connected at their ends to a frame 23 forming the side walls of the; duplicate, key board 7 13.. Each of the key arms 17 are fastened at their'forward end to one of the blocks 65 org66'by rneansv ofa plurality of screws or bolts 71. A key 16 is fastened by any suitable means upon the other end of the arm 17 with the packing plate 63. As best shown in Fig. 3, the arms 17 are made sufficiently thin as to readily yield when the keys 16 are struck. so that they are moved down to the dotted line position of Fig. 3 as a result of a slight stroke by the operative, and yet have suflicient resilience to instantly return following the strokejcausing their depression.

The key arms 17. are arranged in a plurale ity of rows in exactly the same way as the levers 15 of the standard typewriter 10. The keys 16 on the outer end of the arms 17 are positioned immediately above the underlying block 65-. A cushion 64 of rubber or the like is mounted on the upper face of the block 65 to provide a stop for the ends of the arms 17. The cushions 64 not only limit the amount of downward movement of the arms 17,-but also minimize the noise resulting from accidental contact of the arm 17 with the underlying block 65. V The blocks 65 are each providedwith a plurality of ducts 61 and 62. There is a ductv 61 and a duct 62 for each key 16 and key arm 17;, connected with the blocks 65. The ducts 61 and 62' are normally closed by the key arms 17, by reason of packing plates 63 providing air tight closure members as de- A plurality of tubes 59 each connect one of the pipe stems 60 with a corresponding pipe stem 55 mounted in the control action 46. y

The control action 46 comprises upper and lower U-shaped blocks 47 and 48 and a midle 131001149, suitably fastened together to form closed upper chambers 50 anda closed lower chamber 51. The chambers 50 and 51 are normally maintained at reduced air pressure through the medium of an exhaust tube 7 5 leading to a pump (not shown). Each of the pipe stems 55 with which the tubes 59 are connected are mounted in the outer end of one of a plurality of L-shaped ducts 53 and 54. The ducts 53 and 54 have their inner ends terminating in the chambers 50 and 51 respectively. Cooperating with each of the ducts 53 and preferably in alignment thereclose communication with isa corresponding L-shaped duct 94. Similarly each of the ducts 54 have a duct 95 positioned to cooperate therewith. The ducts 94 terminatein the chamber 50 adjacent to the ducts 53 and the ducts 95 similarly terminate in the chamber 51 adjacent to the terminus of a corresponding duct 54. The adjacent terminii of the aligned ducts 53 and 94 and of the aligned ducts 54 and 95 are each covered with a pallet or diaphragm 52. The pallets 52 are shown in Fig. 6 as being open, thereby permitting communication between the ducts having adjoining terminii. It is obvious that collapse of a pallet 52 will between the adjoining ducts whose terminii are covered thereby.

A plurality of tubes 56, corresponding in number with the pneumatics 80, operatively connect each of the pncumatics with one or the other of the ducts 94 and 95 in the control action. 46. Each of the sections or banks 31, 32, 33 and 34 are provided with a plurality of ducts 57, there being one of the ducts for each of the pneumatics 30. A pipe stem 58 is mounted in the outer end of each of the ducts 57. The tubes each connect at one end with a stem 58 and at the other end with a pipe stem mounted in one or the other of the ducts or 95. The ducts 57 are each connected with the reduced air chamber 42 by a relatively small passage 96, as a result of which the ducts 57 and the tubes 56 are normally maintained at the same reduced air pressure as the chamber 42. The reduced pressure in I the chambers 42 is thereby communicated to the tubes 59 and the ducts 61 of the blocks 65.

The depression of a key arm 1.7 resulting "from striking a hey 16 of the duplicate key board opens the connecting duct 61 to the atmosphere. Atmospheric pressure is thereby instantly communicated to the duct 57 through the tubes 59 and 56 in the order named. Atmospheric pressure in the duct 57 forces the pallet 44. to the left, as observed in Fig. 1, and thereby opens the valve 43 to connect the reduced air chamber 42 with the passage As a result, the pressure in the pneumatic is lowered and the pneumatic collapses, thereby actuating the particular key lever 15 corresponding to the depressed l-Iey arm 17 of the duplicate key board. Thus, depression o1 any particular key arm 17 causes the corresponding key lever 15 to strike, the force of such stroke being dependent upon the reduction of pressure in the chambers 42 and the adjustment of the nuts on the connecting rods 37 and 38. Since the pneumatics 30 immediately expand following their collapse, the key lever instantaneously falls away following their stroke.

In order that only one key lever 15 may be actuated at a time. means are provided which prevents the simultaneous collapse of two or more pneumatics 30 should it happen that a second key arm 17 is depressed while the motivating key arm is still depressed.

F or this purpose, I have provided ducts 62 in the blocks 65 in a position to be closed by the key arm 17 when the latter is in its normal position and to be opened when the hey arm is depressed. Each of the ducts 62 have their inner ends opening into a trans Versely extending pipe or duct 72 in the block 65. One end of each of the ducts or pipes 72 is closed. The other ends of the ducts 72 are connected together and with a tube by a plurality of Us 67, Ts 68, and nipples 69.

The tube 70 serves to connect all of the various ducts 62 with a valve 79 positioned in one end of the control action 46. The valve 79 is mounted in a housing forming one end of the control action 46. The housing com prises upper and lower blocks 90 and 91, respectively and an intermediate block 92 so arranged as to provide a closed chamber 98 and a chamber 76 with which the tube 76 connects through a duct 74. The chamber 98 is normally maintained at reduced pressure by the exhaust tube 75 which is connected with an air pump (not shown). The valve 79 comprises outer and inner valve plates 86 and 87, respectively mounted on a stem 88. The valve 7 9 is shown in its normal closed position in Fig. 5, wherein the outer valve plates 86 seal an aperture 80. When the valve 79 is open, air at atmospheric pressure enters the control. action 46 through the aperture and a plurality of connecting apertures 83. The tube 70 and the chamber 76, with which the tube'counects the ducts 62, are at reduced pressure. The chamber 76 is positioned immediately underneath and is separated from the chamber 98 by a pallet 77. At one edge of the pallet "7 is located a bleeder valve, not shown. The bleeder valve normally maintains uniform pressure in the chambers 76 and 98 for a purpose hereinafter more particularly described. The reduced pressure of the chamber 76 permits the pallet 77, which controls the valve 79, to talre the position shown in Fig. 5. Upon depression of any key arm 17, the tube 70 and the chamber 76 immediately underneath the pallet 77 are raised to atmospheric pressure. Atn'iospheric pressure in the chamber 7 6 elevates the pallet 7 7, and with it the valve 79, bringing the valve plates 87 into contact with the lower face of the wall 99, thereby closing oil the chamber 98 and permitting the chamber 98 to remain at reduced pressure. At the same time, the upper valve plates 86 are elevated and permit atmosphere to enter the aperture 80 and the plurality of apertures 83. The chamber 98 meanwhile remains at reduced pressure by reason of the valve plates 87 closing the connection between the apertures 83 and the chamber. The bleeder valve connection between the chambers 76 and 98 is of such capacity that atmospheric pressure to the table 11 by screw bolts underneath the table ating the exists in the chamber 76 sufliciently 'long to elevate the valve 79 to its open position. An instant later the pressure in the chambers 76 and 98 has been suflicientlyequalized through a port 89 connecting the upper chamber 50' with the lower chamber 51. of the control action. Vvhcn the valve '7 9 is open, the chains bers 50 and 51 in the control action 46 are at atmospheric pressure, and thereby flatten each of the pallets In this posltion, the pallets 52 completely close communication between the adjoining ducts 53 and 9 1 and the adjoining ducts 54 and 95. As long as these ducts are closed by flattening the pallets 52 depression of any other key arm17 will not permit atmospheric pressure to trav'eltothe corresponding tube 56 and' duct 57. Smce the corresponding duct 57 remains atreduced pressure, no collapse of the corresponding pneumatic 30 will occur. The valve 79 is closed by the atmospheric pressure in the apertures 83, both the opening and closing occurring in order,-'and substantially instantaneously as long as the key arm17, which initiated the closing of its valve 79, is depressed no further operation of the typewriter key levers will result from depression of the other key arms.

In the embodiment described, the pneuadapted for mounting 11.- The table 11 also supports the typewriter 10'and the duplicate key board 12 with the typewriter and key board fixedly fastened to the table by means of blocks 117. The blocks 117 are fastened 118 an'dto the legs of the typewriter by screw bolts 119 positioned in a socket 120 formedin the block.

In Fig. 8 is shown an alternativeembodiment of theinvention suitable for use in actukey-levers of a movable typewriter machine 100. The machine 100 is supported upon and movable relative to a table 101. In the operation of such'movable machines, the paper or sheets-being typed are fixed relative 7 moves relative to the work.. For the purpose of attaching the-pneumatic actionto such a machine I provide an L shaped supporting frame 103 which is fastened by any suitable means to the frame 102 of the machine. Cantilever arms 10 1 are fastened'to the frame matic action 29 is or billing 103, from which the pneumatic action is sus to the table the machine banks 125, 126, and 127, re

pneumatics 107 are arranged in rows and are connected with the tubes 56 in the same way as already described for the pneumatics 30. Collapse of the pneumatics 30 is accomplished in exactly the same way as for the embodizontally extending rods 113 connects each of the pneumatics 107 with the upper end. of one of a plurality of bell crank levers 110. The levers 110 are pivotally mounted on a rod 111 with the lower free end of the levers in contact with the keys 129 of the key levers 112. The effective lengths of the rods 108 are adjusted bv means of nuts 128 so as to maintain the free ends of the levers 110 normally ment already described. 7 A plurality of horiin contact with the keys 129 of the key levers 112. A rod 113 connects one of the power pneumatics 107 with a lever 11 i. Thejupper endof the lever 114is pivoted on a rod 116 carried by the frame 102. The lower end of the lever 114 normally has bearing contact with a tabulator key 115. The control action 46 described for the fixed typewriter 10 is used with the movable machine 100. The

tubes56 connecting the control ,action 46 with the power pneumatics 107 are flexible and being sufilciently' loose I to permit the maximum movement of the machine 100. It is obvious that collapse ofa pneumatic 107 will actuate a key lever 112 or the tabulator key 115 and that this embodiment of the invention is particularly adapted for use with a movable, typewriter. V

In Figs. 9 and 10, still another modification of the device is illustrated as applied to a plurality of typewriting machines. table 11,has mounted thereon,,in addition to the manual or duplicate key board 13, a plurality of standard typewriting machines designated by the numerals 10- 10-0 and 10D, respectively. The manual or duplicate key board 13 is connected with each of the typewriting machinesby the control action 46 so as to simultaneously operate A, 10B, o

The a tuation of the corresponding key arms 17 of the duplicate key board. For this purpose the duplicate key board 13 is connected with the control action 46 by altube 70 and a-plurality of tubes 59 substantially as already shown and from the control action 16 are substantially the same in construction and the same in number as provided for the embodiments already described. Each 56-D The tubes 56A are all operatively connected with power pneumatics 30 which control the key levers of the typewriting machine 10-A. The divisional tubes 56-B are likewise operatively connected with the power pneumatics 30 controlling the key levers 15 of the typewriting machine 10-B. Simlarly, the divisional tubes 56-C and of the tubes 56. branch into 56 A tubes, 56-13, 56,C and described. Thetubes 56 leading 56D control the power neumatics 30 of the typcwriting machines 10-C- and 10D, respectively. As thus arranged, it is obvious that each of the plurality of t-ypewriting machines 10 may be controlled by a single opadjusted to produce the maximum number of carbon copies. The limit of such copies is the maximum amount of force with which the key lever can strike, wthout puncturing the original sheet. This production of a large number of carbon copies by a single operation is accomplished without requiring the operative to exercise any additional energy in actuating the flexible key arms 17. This application of the invention simultaneously to a plurality of typewriting machines enables a single operative to turn out as many sheets as may be desired by simply increasing the number of machines which are connected with the control action 46.

Having thus described my invention, it is obvious that various immaterial modifications may be made in the same without departing from the spirit of my invention; hence, I do not wish to be understood as limiting myself to the exact form construction, arrangement and combination of parts herein described and shown, or uses mentioned.

hat I claim as new and desire to secure by 1 Letters Patent is:

ed with one of said key levers by a rod, one

end of each rod being adjustably fastened to one of said power pneumatics and the other end of each rod forming a hook engaging a corresponding key lever, collapse of said pneumatics causing the rods to actuate the key lever connected therewith and expansion of the pneumatic permitting the hooked end of the rod to move independently of the key lever, control mechanism for the power pneumatics comprising a duplicate key board, a plurality of tubes normally at low pressure each ope-ratively connecting an individual key lever of the duplicate key board with a power pneumatic, whereby actuation of a duplicate key lever causes the corresponding power pneumatic to collapse and actuate its typewriter key lever, and pneumatic means operable to prevent the simultaneous collapse of two power pneumati cs.

2. An attachment for typewriting machines, comprising a duplicate key board and pneumatic mechanism operatively connecting the duplicate key board with the typewriting machine whereby said machine is selectively actuated by means of the duplicate key board, said pneumatic mechanism comprising a plurality of-power pneumatics each operable on collapse to actuatea typewriter key lever, a, plurality of tubes each connecting one of said power pneumatics with a corresponding key lever of the duplicate key board, a reduced pressure conduit with which each of the duplicate key board levers is connected, means normally maintaining said tubes and conduit at reduced pressure, means initially o ierable upon actuation of a key lever of the duplicate key board to open the corresponding tube to atmospheric pressure and thereby cause the collapse of the corresponding power pneumatic, a control action through which each of said tubes pass, means whereby said actuation of a duplicate key board lever also opens said conduit to atmospheric pressure, said control action comprising means operable upon opening said conduit to the atmosphere, to close all of said tubes and thereby prevent changed pressure conditions therein between said control action and said power pneumatics, said closure immediately following the collapse of any power pneumatic.

3. An attachment for typewriting machines, comprising a duplicate key board and pneumatic mechanism operatively connecting the duplicate key board with the typewriting machine whereby said machine is selectively actuated by means of the duplicate key board, said pneumatic mechanism comprising a plurality of power pneumatics each operable on collapse to actuate a typewriter key lever, a plurality of tubes each connecting one of said power pneumatics with a corresponding key lover of the duplicate key board, a reduced pressure conduit with which each of the duplicate key board levers is connected, means normally maintaining said tubes and conduit at reduced pressure, means initially operable upon actuation of a key lever of the duplicate key board to open the corresponding tube to atmospheric pressure and thereby cause the collapse of the corresponding power pneumatic, said actuation of a duplicate key board lever also opening said conduit to atmospheric pressure, a control action through which each of said tubes pass, said action comprising a system of valves each operable to close one of said tubes, said valves being moved to closed position and remaining closed when said conduit is open to atmospheric pressure.

4. An attachment for typewriting' machines, comprising a duplicate key board and H pneumatic mechanism operatively connecting the duplicate key board with the typewriting machine whereby said machine is selectively actuated by means of the duplicate key board, said pneumatic mechanism comprising a plurality of power pneumatics each operable on collapse to actuate a typewriter key lever, a plurality of tubes each connecting one of said power pneumatics with a corresponding key lever of the duplicate key board, a reduced pressure conduit with which each of the duplicate key board levers is connected, means normally maintaining said tubes and conduit at reduced pressure, means initially operable upon actuation of a key lever of the duplicate key board to open the corresponding tube to atmospheric pressure and thereby cause the collapse of the corresponding power pneumatic means whereby said actuation of a duplicate key board lever also opens said conduit to atmospheric pressure, a control action with which each of said tubes is connected, said control action comprising a system of valves each connected with one of said tubes, said valves being moved to closed position and remaining closed while the conduit is at atmospheric pressure, said closure of the valves following immediately after the collapse of a power pneumatic and remaining in closed position until the actuating duplicate key board lever has returned to its original position.

In witness whereof, I hereunto subscribe my name this 8th day of July A. D., 1929.

SELVIYOR A. SWANSON. 

